Cardiac arrest in marathons and triathlons

Your Heart Health in a Heartbeat – Episode 6


Cardiac arrest during marathons: 10 facts to consider.

Study of triathlon deaths concludes more screening is needed.

Interesting research studies from the American College of Cardiology 2016 meeting.


Hello everyone,

There has been bad news coming from the marathon and triathlon communities regarding cardiac deaths during these events.  At the London marathon, a middle aged man suffered a cardiac arrest, and in Canada, a few days ago, a middle-aged woman also had a cardiac arrest and died during the swim portion of a triathlon.

So I thought I would take a few minutes today to go over what we know about cardiac arrest at these endurance events, and then go over some new recommendations for screening that were proposed at a recent meeting of the American College of Cardiology.

So first, the marathons.  A few years ago, an important paper was published that looked at cardiac arrests occurring during marathons over a 10-year period.  Let me give you five highlights from that paper:

First, cardiac arrest is much more common in men than in women, by a factor of 9-to-1.

Second, the average age was 43, but the age range was wide, from 22 to 65 years of age

Third, the frequency has been increasing over the years.  That is likely because more people are participating in these kinds of events, and some of the participants are older than in the past.

Fourth, most cardiac arrests occur in the last third of a marathon.  That’s probably because of strain and exhaustion as contributing factors, or possibly electrolyte shifts.  The cardiac arrest that occurred in the London marathon occurred near the end of the race.

Fifth, in most cases, the victims were found to have had a pre-existing heart condition they were unaware of, most commonly a disease of the heart muscle, called cardiomyopathy, or a disease of the coronary arteries.

I wrote a more complete blog post on this topic and I will link to it in the show notes on the website.

Now, as far as triathlon events are concerned, a study was presented a few weeks ago at the American College of Cardiology’s scientific meeting.  The study was led by Dr. Larry Creswell, a heart surgeon who is also a triathlete and has written extensively on cardiac complications in athletes.

The study is not published yet, but I can summarize the main findings as they were reported:  First, the demographics were similar to those of the marathon study: average age in the mid 40’s and mostly men.  Secondly, most deaths occurred during the swim portion of the event.  Thirdly, like in the marathon study, many of the cardiac arrest cases had an identifiable pre-existing condition that could have been detected by screening.  On the basis of those findings, the investigator recommended that middle-aged should consider heart screening before these events.

That said, we should add that how you do the screening matters.  If you are going to screen with just an ECG or a routine physical, that may not be enough to pick up the conditions we’re interested in that might lead to cardiac arrest.  It is important that the screening be thorough.